1. Field of the Invention
This invention relates to injecting one or more phases of steam into one or more formations from a single string of tubing by utilizing an impingement means in a side pocket mandrel or other downhole tools and including, if desired, an agitation device to control the quality and flow of steam. The invention may also include a centralizer to guide a tool string and disperse the steam.
2. Description of Related Art
In the past, various configurations of devices were used to inject steam and other fluids and gases into one or more zones of a formation to enhance hydrocarbon recovery, such as oil, from the earth. Depending on the medium injected and the properties of the formation, some of these devices were more successful than others.
Early injection techniques usually involved drilling a hole for each formation zone in a selected area. This horizontal expansion method of enhanced recovery is extremely expensive and time-consuming. A more economical method would entail servicing the various zones in a formation by way of multiple injection points in a single drilled hole.
A related patent, U.S. Pat. No. 4,248,302, answering the need for multiple zone injection from a single drilled hole was granted to Ronald K. Churchman and was assigned to Otis Engineering Corporation. Although particularly addressing pumpdown (through the flow line) completions, the patent does show using one or more side pocket mandrels to inject fluids and steam into one or more wells and/or formation zones. This method and apparatus was an advancement in the field of steam injection.
As interest in injection increased, several zones in a formation were serviced from a single drilled hole by utilizing concentric tubing. Such a configuration is shown in U.S. Pat. No. 3,319,717 by D. V. Chenoweth, U.S. Pat. Nos. 4,081,032, 4,099,563 and 4,399,865 by S. O. Hutchinson and G. W. Anderson and U.S. Pat. No. 4,081,028 by E. E. Rogers. All these devices allow steam or hot fluids to flow through the inner tubing to the next distributing apparatus while providing a passage for the steam or hot fluids to flow into the casing-tubing annulus and into a selected zone. While an improvement on multiwells, these devices did not allow the operator to deliver a calculated percentage of steam and hot fluid to a particular zone nor did they control the quality of the steam at several points in the well bore. Also the operator could not run maintenance tools down the tubing string to rework the downhole devices. Testing of this type of device showed that heat transfer between the concentric tubes created a heat loss from one tube to the other and created undesirable tubing movement. Chenoweth's U.S. Pat. No. 3,319,717 device was retrievable but had to be removed from the tubing string before any survey or maintenance tools could be run below the device. Oilfield operators wanted a system more controllable and more easily maintained.
U.S. Pat. No. 3,455,382 by D. V. Chenoweth solved part of the maintenance problem by injecting into different zones with a pressure regulator placed in a side pocket material. Tools to service the downhole devices could then be passed by the pressure regulators without removing them. The function of the pressure regulators was to keep the single phase injection fluids going through the exit port in the side pocket mandrel and into the tubing-casing annulus at a constant rate regardless of tubing pressure upstream or downstream of the pressure regulator. However, Chenoweth's device did not address the problem of providing a desired percentage of vapor and hot fluids to one or more separate formation zones. This device did not, because of its throttle-like action, allow the user to calculate a critical flow relationship utilizing known input pressures of injected fluid or steam. The present invention does allow the user to calculate a critical flow relationship and also has the advantage of having no moving parts.